His phase templar
The damage reduction is the same when removing all costs, but the Phase Templar is more centered around the prevention of attack than taking less damage. If anything, you could compare both of these cards to Moomoose's Treant when considering damage reduction alone.
Acceleration | Overdrive, anyone?
An initial cost of 3 | 5 , then 1 per turn to gain +2 | +3 attack each turn?
Over time, it's cheaper than growth. And Overdrive is 4 , not 5.
So What does that all mean?
Basically a cheaper and stronger growth mechanic that is available to Rock Golem | Boulder Golem via Acceleration | Overdrive.
Cheaper and stronger?
Best case scenario it is
Overdrive + Rock Golem
4
+ 3
+ 1 upgrade + 2 cards ~= 9
+ Duo + 1 upgrade + 1 card [Lava Destroyer is 5
+ Duo + 1upgrade + 1card]
for
3|2
: +3|+0 [Lava Destroyer is 7|1
: +2|+2]
Summary: Cost is about 4 quanta more for -4 attack and +3|+0 rather than +2|+2